Improved check is_open_canonical_projection

The check looks for 1 canonical projection applied to a meta/evar.
This fails to deal with telescopes that generate unification problems
containing something like "(pi_1 (pi_2 ?))" that is indeed a "stuck"
canonical projection but not of the form recognized by the previous
implementation. The same holds when pi_2 is a general function not
producing a constructor.

This patch checks if the argument of the canonical projection weak head
reduces to a constructor calling whd_betadeltaiota.

git-svn-id: svn+ssh://scm.gforge.inria.fr/svn/coq/trunk@14645 85f007b7-540e-0410-9357-904b9bb8a0f7

1 files changed, 12 insertions, 0 deletions

diff --git a/test-suite/success/telescope_canonical.v b/test-suite/success/telescope_canonical.v
new file mode 100644
index 000000000..8a607c936
--- /dev/null
+++ b/test-suite/success/telescope_canonical.v
@@ -0,0 +1,12 @@
+Structure Inner := mkI { is :> Type }.
+Structure Outer := mkO { os :> Inner }.
+
+Canonical Structure natInner := mkI nat.
+Canonical Structure natOuter := mkO natInner.
+
+Definition hidden_nat := nat.
+
+Axiom P : forall S : Outer, is (os S) -> Prop.
+
+Lemma foo (n : hidden_nat) : P _ n.
+Admitted.